碩士 / 國立中央大學 / 遙測科技碩士學位學程 / 107 / Deep convection plays an important role in the global climate. It affects not only the balance of radiation and the hydrological cycle but also transports polluted particles, energy and moisture from the boundary layer to the upper atmosphere, which might link to the greenhouse effect. We conduct the analysis of CloudSat and ERA-Interim data from 2007 to 2016, to identify the deep convective systems (DCS) over the Maritime Continent (MC) and the South China Sea (SCS). The associated vertical structure, horizontal span, dynamic environmental factors, and spatial and temporal characteristics of deep convection were analyzed to seek the possible atmosphere dynamic controls of deep convection in the targeting regions.
The results show that more isolated convective systems formed at MC (0.74% incidence) with more packed and larger particles at the upper-convective core (CTH-H_10dBZ: 3.43km). There are more organized convections formed over SCS (0.88% incidence) with more dispersed and smaller particles at the upper-convective core (CTH-H_10dBZ: 3.77km). The system horizontal span and echo height difference, rising velocity and the upper-level divergence are all positively correlated, especially, the deep convective core is highly sensitive to the ascending motion and the upper-level divergence (10-16 km). The vertical wind shear (VWS) less than 20ms-1 may increase the horizontal size of DCS, which is beneficial to the development of mesoscale systems. However, VWS over than 20ms-1 disperses the structure of the convective cloud, decreasing the occurrence frequency of the isolated system. Also, 10 km height is a critical threshold level, where the maximum vertical updraft velocity and the upper-level divergence.
According to the land-sea distribution, diurnal variation and vertical dynamic structure of DCS, that there might be two different formation mechanisms for convective systems: 1) the boundary layer becomes unstable due to surface heating in the afternoon, and the isolated systems (S-type; <300km) are formed which characterized by small echo-top height difference (~3km) and strong lower-level (2-8 km) ascending motion which transports the large particles from the bottom to the upper level; 2) Boundary-layer cloud radiative cooling destabilizes the low-layer atmosphere, creating a favorable condition for shallow convection to develop to deep convection in the nighttime and over the ocean. Isolated or organized convective system （L-type; >300km） formed under this condition which characterizes with larger echo-top height differences (~4km).
| Identifer | oai:union.ndltd.org:TW/107NCU05105011 |
| Date | January 2019 |
| Creators | hao, 陳恩浩 |
| Contributors | Chian-Yi Liu, 劉千義 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | en_US |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 76 |
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